Earthen reservoir with frozen roof covering and method of forming the same



Dec. 26, 1967 G. F. BISHOP 3,359,739

EAR'IHEN RESERVOIR WITH FROZEN ROOF COVERING AND METHOD OF FORMING THE SAME Filed 001;. 11, 1963 6 Sheets-Sheet 1 INVENTOR.

G. F. L. BISHOP BY 4a? A TTORNE KS Dec. 26, 1967 cs. F. 1.. BISHOP 3,359,739

EARTHEN RESERVOIR WITH FROZEN ROOF COVERING AND METHOD OF FORMING THE SAME G.F.L.BISHOP A T TORNEI S Dec. 26, 1967 G. F. L. BISHOP 3,359,739

EARTHEN RESERVOIR WITH FROZEN ROOF COVERING AND METHOD OF FORMING THE SAME Filed Oct. 11, 1963 5 Sheets-Sheet 5 ATTORNEYS mm P f q w wm mm wm mm S mm mm United States Patent 3 359 739 EARTHEN RESERVOIR wiTH FROZEN ROOF cov- ERING AND METHOD OF FORMING THE SAME George F. L. Bishop, Woods Cross, Utah, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Oct. 11, 1963, Ser. No. 315,607 Claims. (Cl. 61.5)

This invention relates to the storage of volatile liquids in an earthen reservoir. In one aspect this invention relates to a method for forming an earthen reservoir for storage of volatile liquids in a geographical area subject to seasonal freezing temperatures. In another aspect this invention relates to an earthen reservoir for the storage of volatile liquids having a natural ice roof.

Storage of volatile liquids such as liquefied hydrocarbon gases in earthen reservoirs has been proposed. These proposals have necessitated freezing the earth by artificial means to construct the cavity and covering the top of the cavity with a steel or artificial ice roof. When an artificial ice roof is constructed, the freezing equipment, such as pipes, coils, and the like, becomes frozen into the ice roof and therefore must be considered expendable in the preparation of such storage reservoir.

According to my invention an earthen storage reservoir is formed utilizing a cavity excavated in the earths surface, or a natural cavity if such is available, that is filled with water during a seasonal period of freezing temperature so as to form an ice crust on the surface of the water and this ice crust is then built up to the required thickness by the incremental addition of water to the upper surface of the ice crust so that the thickness of the ice crust is increased to the desired value. In order that equipment for introduction and withdrawal of fluids from the cavity may be placed in position during the preparation of the reservoir, a load-bearing beam is placed across the upper portion of the reservoir and then this beam is encased in the ice crust as it is formed. The surface edge of the cavity is beveled outwardly so that the ice crust is supported by the cavity walls when the water is removed. A positive gas pressure can be maintained in the reservoir sufiicient to support, or at least partly support, the ice crust which forms the roof of the reservoir.

It is an object of this invention to provide a method for forming an earthen reservoir for the storage of volatile liquids in a geographical area subject to seasonal freezing conditions. Another object of the invention is to provide an earthen reservoir for the storage of volatile liquids having a natural ice roof. Still another object of the invention is to provide an earthen reservoir for the storage of volatile liquids having a natural ice roof which is maintained in frozen condition during seasonal periods when the temperature is above freezing. Other objects, advantages and features of the invention will be apparent to those skilled in the art upon study of the disclosure of the invention including the detailed description and the appended drawing wherein:

FIGURE 1 is a plan view of an earthen reservoir according to this invention;

FIGURE 2 is a view along lines 2-2 of FIGURE 1;

FIGURE 3 is a view along lines 3-3 of FIGURE 1; and

FIGURE 4 is a modification of the invention as shown in FIGURE 3.

Referring now to FIGURE 1, a rectangular cavity is shown having beveled edges 11 sloping inwardly from the earths surface to the wall of the cavity 10. A loadbearing beam 12 is positioned across the upper part of the cavity so as to rest on the walls 13 of the cavity with the bottom of the beam about level with the bottom of the bevel 11. A deep well pump 14 is supported on the beam 12. Fluid inlet openings 15 and a vapor vent opening 16 are also provided in the beam 12.

FIGURE 2 shows a sectional elevation of the reservoir of FIGURE 1 with the ice crust 17 covered by a layer of insulation 18. Cold volatile liquid is passed via conduit 19 through opening 15 to spray header 21 having a plurality of sprays 22 to spray liquid upwardly against the bottom of the ice crust 17 and outwardly over the Wall 13 of the cavity so as to maintain the ice crust and the cavity walls frozen during seasonal periods of temperatures which are higher than freezing. Deep well pump 14 removes volatile liquid from the reservoir via conduit 23 as required. Conduit 24 removes vapor from the vent 16 for consumption or to be compressed, cooled and returned to the reservoir via conduit 19.

FIGURE 3 illustrates more fully a preferred piping arrangement for the reservoir of FIGURE 1. The deep well pump 14 with its motor 25 is supported on beam 12 through a sleeve 26 having a means 27 for vertical adjustrnent of the pump 14 in the sleeve 26. Liquid removed from the reservoir 10 by means of pump 14 passes via conduit 23 and conduit 28, containing valve 29, for consumption or for market as desired. Liquid removed from reservoir 10 by pump 14 can also be passed via conduit 23, conduit 31, valve 32 and conduit 19 to spray header 21 containing sprays 22.

Liquid, cooled in cooler 47, is introduced to the cavity from an outside source such as a tank car, distillation column, and the like, via conduit 33, pressure control valve 34, conduit 19 and spray header 21 or via conduit 35 containing valve 36 so as to by-pass, at least partially, the spray header 21. Valve 36 in conduit 35 and valve 37 in conduit 19 can be so regulated that flow will pass through both conduits 19 and 35.

Vapor is withdrawn from the cavity via conduit 24 containlng pressure relief valve 38 which allows vapor to be vented to stack 39 when the pressure of the vapor in the cavity 10 exceeds a preset pressure, for example, 2 pounds gage, i.e., 2 pounds per square inch in excess of atmospheric pressure. Vapor is withdrawn from conduit 24 via conduit 41, compressed in compressor 42, cooled in cooler 43 and then passed as liquid via conduit 44 and valve 45 to conduit 33 to be recycled through spray header 21. Heat can be removed from the reservoir, continuous-ly or intermittently, by thus compressing and cooling the vapors evolved from the liquid in the reservoir.

A modification of the reservoir of the invention for utilizing an exceptionally large pit, e.g., one having a horizontal dimension greater than about 100 feet, is shown in FIGURE 4. Such installation might utilize a quarry or shale pit. In this modification vertical supports indicated at 51 can be erected to support the load-bearing beam 12. Additional supports indicated at 52 can be placed in the cavity so as to terminate at their upper ends at about the lower surface of the ice crust so as to provide support for the ice crust. In this modification liquid can be removed from the reservoir by a gas lift device 53 com-' prising a conduit 54 and a gas injection pipe 55. The liquid and the carrier gas pass via conduit 56 to liquid gas compressor 59 and returned via gas injection pipe 55 to the removed from separator 57 via conduit 58, compressed in compressor 59 and return via gas injection pipe 55 to the gas lift device. The use of the gas lift device avoids the necessity of supporting heavy pumping equipment on the beam 12. The auxiliary supports can be concrete columns as illustrated or can be piles of rocks, earth and the like.

The load-bearing beam 12 of the drawing will preferably be prestressed, reinforced concrete but can be ordinary steel beams, junk pipe, railroad rails, and the like.

The deep well pump of FIGURES 2 and 3 can be any conventional deep well pump capable of being moved vertically a few inches. One such arrangement for mounting such pump is shown in US. Patent 2,842,208, issued July 8, 1958, to H. H. Dukes. Gas lift systems such as that shown in FIGURE 4 are well known and one such system is shown in US. Patent 1,102,152, issued June 30, 1914.

The ice roof can be strengthened for long unsupported spans by reinforcing the ice crust as it is being formed by the addition of water to the top of the ice crust by including excelsior, hay, metal bars and rods, woven metals such as chain-length fence, and the like, in the ice crust. Another method for strengthening the ice crust is to increase the thickness of the ice at the center of the span by adding water to the center of the ice-covered cavity during the period of freezing weather when the ice crust is being formed so that the ice crust is thicker in the center with the result that a cross section of the ice crust approximates the configuration of a plano-convex lens. A combination of these methods can also be employed.

The beveled edges of the earthen cavity allow the weight of the ice crust to be borne by the walls of the cavity and also allow expansion and contraction of the ice crust with very little vertical displacement of the ice crust.

The invention will now be described in the following example as applied to specific dimensions and conditions which are presented as being typical and therefore this example should not be construed to limit the invention unduly.

Example A cavity is excavated in the earths surface in the form of a rectangle about 35 feet long and 20 feet wide to a depth of about 40 feet. A bevel is formed around the periphery of the cavity about 45 degrees from horizontal and extending from the earths surface downwardly to the wall of the cavity about 5 feet below the earths surface. A prestressed reinforced concrete beam about 6 feet in width is placed across the top of the cavity so as to rest on the beveled edges of the cavity with the bottom of the beam about 2 feet above the bottom of the beveled edge of the cavity. The beveled sides of the cavity are recessed as necessary to provide a solid footing for the beam. The beam has vertical openings therethrough for installation of a deep well pump and fluid inlet and outlet conduits. The deep well pump is installed and connected; the spray header is installed and positioned so as to be below the ice crust formed across the top of the cavity; the liquid inlet conduit is installed; and the vapor outlet conduit is installed. The cavity is filled with water to a point just below the prestressed concrete beam during the period of freezing temperature and a crust of ice about 2 to 3 inches in thickness is allowed to form over the surface of the water. Water is then added to the top surface of the ice crust, e.g., with a hose at a rate such that the water added to the ice crust will freeze as it is added until the thickness of the ice crust has been increased to about 3 feet and the concrete beam is cornpletely encased in the ice crust. Hay is added along with the water to the surface of the ice to provide reinforcement for the ice crust. The ice crust is then covered with an insulating layer of sawdust about 1 foot in thickness and the sawdust is then covered with a polyethylene tarpaulin so as to maintain the sawdust dry. The tarpaulincovered sawdust insulation extends about 10 feet beyond the edge of the cavity in each direction.

When all of the auxiliary equipment such as the refrigeration system comprising compressor and cooler are installed, the water is pumped from the cavity and gas is introduced into the cavity in an amount sufiicient to maintain a gas pressure within the cavity of about 2 psi. gage. A pressure of about 2 pounds gage will substantially support the ice roof so that the ice roof is, in effect, floating on a body of gas. As soon as the water is pumped out from the cavity, the pump. is raised a few inches to clear the water at the bottom of the cavity and the volatile liquid, e.g., liquid propane, is introduced into the cavity through the spray header so that the cold liquid is sprayed upwardly against the ice roof and outwardly so as to run down the wet walls with the result that the water on the walls and floor of the cavity is frozen to provide a vaportight frozen reservoir. The refrigeration system is started as soon as the filling of the reservoir is started so that the vapor, resulting from cooling the reservoir down to about -45 F., is compressed, cooled to about 45 F. and returned to the reservoir as liquid propane. The liquid propane from a tank car, distillation column or other source is cooled to about 45 F. before being introduced to the reservoir.

That which is claimed is:

1. The method of preparing an earthen reservoir for the storage of volatile liquids in a geographical area subject to seasonal freezing atmospheric temperatures which comprises the steps of excavating a cavity in the earths surface; placing a pre-stressed concrete beam across the top of the cavity; installing a discharge pump in said cavity so as to be supported by said beam; installing a conduit for introducing liquid to the cavity through said beam; installing a conduit for venting vapor from the cavity through the beam; filling the cavity with water to the bottom of said beam; subjecting the surface of the water to freezing atmospheric temperature so as to freeze a crust of ice on the surface of the water; adding water .to the top of the ice crust; subjecting the added water to freezing atmospheric temperature to form an ice crust about 2 to 3 feet in thickness; covering the top of the ice crust with a layer of insulation; pumping the water from the cavity; adding volatile liquid to the wet cavity; and venting vapor from the cavity.

2. The method of preparing an earthen reservoir for the storage of volatile liquids in a geographical area subject to seasonal freezing atmospheric temperatures which comprises the steps of forming an outwardly slop-ing bevel about the periphery of a cavity in the earths surface; placing a beam across the top of the cavity; installing a discharge pump in said cavity so as to be supported by said beam; installing a conduit for introducing liquid to the cavity through said beam; installing a conduit for venting vapor from the cavity through the beam; filling the cavity with water to the bottom of said beam; subjecting the surface of the water to freezing atmospheric temperature so as to freeze a crust of ice on the surface of the water; adding water to the top of the ice crust; subjecting the added water to freezing atmospheric temperature to form an ice crust about 2 to 3 feet in thickness; covering the top of the ice crust with a layer of insulation; pumping the water from the cavity; adding volatile liquid to the wet cavity; and venting vapor from the cavity.

3. The method of preparing an earthen reservoir for the storage of volatile liquids in a geographical area subject to seasonal freezing atmospheric temperatures which comprises the steps of placing a load-bearing beam across the open top of a cavity in the earths surface with the bottom of the beam 2 to 3 feet below the earths surface; supporting on said beam means to introduce volatile liquid into and withdraw volatile liquid from said cavity; filling the cavity with water to the bottom of said beam during the season of freezing atmospheric temperature so as to freeze a crust of ice on the surface of the water; adding increments of water to the surface of the ice crust so as to freeze a solid ice crust about 3 feet in thickness; covering the top of the ice crust with a layer of insulation; removing the water from the cavity while addin gas to said cavity to maintain a vapor pressure suflicient to support, at least partly, the crust of ice; adding volatile liquid to the wet cavity; venting vapor from the cavity; and spraying volatile liquid onto the lower surface of the ice crust.

4. The method of preparing an earthen reservoir for the storage of volatile liquids at substantially atmospheric pressure in a geographical area subject to freezing atmospheric temperature which comprises forming a bevel around the periphery of an open cavity in the earths surface sloping from the surface inwardly to the wall of the cavity about 5 feet below the surface; placing a load bearing beam across the .top of the cavity with the bottom of the beam about 3 feet below the earths surface; supporting on said beam fluid inlet means and fluid outlet means; filling said cavity with water to the bottom of said beam during the season of freezing atmospheric temperature so as to freeze a crust of ice on the surface of the water; adding increments of water onto the ice crust so as to freeze a solid ice crust about 3 feet in thickness; covering the ice crust with a layer of insulation; removing water from the cavity; adding gas to said cavity while removing the water so as to maintain gas pressure in said cavity suflicient to support the ice crust and insulation; adding volatile liquid to the wet cavity; spraying volatile liquid onto the lower surface of the ice crust; and removing gas from said cavity that is not required to maintain suflicient pressure to support the ice crust and insulation.

5. An earthen reservoir for the storage of volatile liquids at substantially atmospheric pressure which comprises an open-topped cavity in the earths surface having a beveled top from the earths surface sloping inwardly to the wall of the cavity about 5 feet below the earths surface; a load-bearing beam positioned across the upper portion of said cavity; fluid inlet and outlet means supported upon said beam; a crust of natural ice covering said cavity and encasing said beam; a layer of insulation covering said ice crust; means to spray volatile liquid onto the lower surface of said ice crust; and means to maintain an ice crust-supporting gas pressure in said reservoir.

References Cited UNITED STATES PATENTS 99,911 2/1870 Kerr 61-30 1,495,310 5/1924 Stromborg 6146 2,961,840 11/1960 Goldtrap 61-.5 X 3,129,565 4/1964 Bellamy 61--1 3,205,665 9/ 1965 Van Horn 61.5

FOREIGN PATENTS 26,145 1/ 1953 Finland.

EARL J. WITMER, Primary Examiner. 

1. THE METHOD OF PREPARING AN EARTHEN RESERVOIR FOR THE STORAGE OF VOLATILE LIQUIDS IN A GEOGRAPHICAL AREA SUBJECT TO SEASONAL FREEZING ATMOSPHERIC TEMPERATURES WHICH COMPRISES THE STEPS OF EXCAVATING A CAVITY IN THE EARTH''S SURFACE; PLACING A PRE-STRESSED CONCRETE BEAM ACROSS THE TOP OF THE CAVITY; INSTALLING A DISCHARGE PUMP IN SIDE CAVITY SO AS TO BE SUPPORTED BY SAID BEAM; INSTALLING A CONDUIT FOR INTRODUCING LIQUID TO THE CAVITY THROUGH SAID BEAM; INSTALLING A CONDUIT FOR VENTING VAPOR FROM THE CAVITY THROUGH THE BEAM; FILLING THE CAVITY WITH WATER TO THE BOTTOM OF SAID BEAM; SUBJECTING THE SURFACE OF THE WATER TO FREEZING ATMOSPHERIC TEMPERATURE SO AS TO FREEZE A CRUST OF ICE ON THE SURFACE OF THE WATER; ADDING WATER TO THE TOP OF THE ICE CRUST; SUBJECTING THE ADDED WATER TO FREEZING ATMOSPHERIC TEMPERATURE TO FORM AN ICE CRUST 